Field
Embodiments described generally relate to strengthening resins for paper products. More particularly, such embodiments relate to strengthening resins that can include a polyamide-epihalohydrin (PAE) resin, a cationic styrene maleimide (SMI) resin, and a urea-formaldehyde (UF) resin, products made therewith, and methods for making and using same.
Description of the Related Art
Paper is sheet material containing small, discrete fibers interconnected with one another. The fibers are usually formed into the sheet material on a fine screen from a dilute water suspension or slurry. The paper can typically be made from cellulosic fibers; however, synthetic fibers can also be used. The wet strength of paper generally refers to the resistance of paper to rupture or disintegrate when wetted with water. Paper products made from untreated cellulosic fibers exhibit a rapid decrease in wet strength when contacted with water and are generally characterized as having a low wet strength. The wet strength of a paper product made from untreated cellulosic fibers is generally only about 5% of a dry strength of the paper product. Various methods for treating the paper products and the cellulose fibers thereof have been employed to increase the wet and/or dry strength thereof. For example, strengthening, resins such as wet and/or dry strengthening resins, can often be applied to the cellulose fibers of the paper products to increase the wet and/or dry strength thereof.
The wet strengthening resins applied to the paper can be categorized as either a “permanent” type resin or a “temporary” type resin, which can be determined by the amount of time the paper retains its wet strength after contact with or immersion in water. While the wet strength retention of a paper product is a desirable property for certain applications, paper products that utilize “permanent” type wet strengthening resins often exhibit poor resistance to rupture or degradation. For example, paper products utilizing the “permanent” type wet strengthening resins can often be degraded only under undesirably severe conditions. Further, while the paper products treated with the wet strengthening resins exhibit increased wet strength, the dry strength of the paper products is generally unaffected or insignificantly increased, thereby limiting their utility in applications where both wet and dry strength is desired such as for use as packaging.
There is a need, therefore, for improved strengthening resins, products made therewith, and methods for making and using same.